Social hierarchy of society?

Why is the social hierarchy of high school the way it is? Im in junior in high school and im in the middle(not popular, not a nerd) and it annoys me how some people ignore or just refuse to speak to anyone that isn't in their social status. I understand if you don't like someone from a certain reason. Basically i hate arrogance and ignorance and how the fudge did we get to this point of intolerance?